1. Field of the Invention
The present invention relates to a GaAs semiconductor substrate suitably used as a substrate for a group III-V compound semiconductor device and a method of manufacturing the same, and to a group III-V compound semiconductor device including the GaAs semiconductor substrate and a method of manufacturing the same.
2. Description of the Background Art
GaAs semiconductor substrates have been widely used as substrates for group III-V compound semiconductor devices such as an LED (light emitting diode), an LD (laser diode), and the like. A group III-V compound semiconductor device is obtained by forming one or more group III-V compound semiconductor layers on a main surface of a GaAs semiconductor substrate.
If an acid substance as an impurity is present in large amounts on a main surface of a GaAs semiconductor substrate, the main surface becomes rough. A shape defect occurs in a group III-V compound semiconductor layer formed on the rough main surface of the GaAs semiconductor substrate. Therefore, a yield of a group III-V compound semiconductor device is reduced.
Consequently, to increase a yield of a group III-V compound semiconductor device, for example, a group III-V compound semiconductor wafer in which the number of atoms of an acid substance on a polished and cleaned surface is not more than 5×1012 per cm2, and a method of manufacturing the same have been proposed (see Japanese Patent No. 3480411 (Japanese Patent Laying-Open No. 2001-223191)).